Atmospheric air flow regulator



Sept. 12, 1944.

G. TQSIMPSON 'l 2,358,260 HERIC AIR FLOW REG LATA R Filed `April l5, 1941 2 Sheets-Sheet 1 sept. 12, 1944.

G. T. SIMPSON l ATMOSPHERIC AIR FLOW REGULATOR 2 Sheets-Sheet 2 Filed April l5, 1941 Patented Sept. l2, 1944 UNITED.

STATI-:sh- APa'rlfzlv'r orifice ATMO SPHERIC AIR FLOW RJilGrJlnTOR-- Y George T. Simpson, Detroit, Mich.

Application' April 15, 1941, Serial No. `388,663`

` In Canada June 8, I1940 8 Claims.

mosphericair ow regulators which function'by the force 'due to the velocity of owing air, as `a windmill does, as distinguished from those regulators which function bythe expansive force of a compressed iiuid, as a steam engine does; and,' specifically, `to those regulators^ in which the damper has its Vaxis at one of its edges. The ob- Vjectsof` my improvements are, rst, to minimizel the 4loss of velocityin the air owing through the regulator when the force foff theair tok be con-` AVAtrolled is low); second, to provide a regulator designed to control the flow of air down to a delivered velocity as low as 200 -feet per minute, or

lower; third, to `provide adesign and method by v which the dimensions of any size of regulator' can be determinedwithout resorting wholly to experimentation; fourth, `to provide a much `greater range of regulation than has hitherto been knownyfth, to provide a means by which the damper would be restrained from leaving its full open position until the desired quantity of (Cl. My invention relates to improvements in at-i kin vwhich the vdamper' hangs plumb when in its full open position, in a housing having a bottom Wall that` is shaped as an irregular curve.`

The two side walls l, `l vwith the anguiarshaped' piece 2, the 90 degreecurved removable top ri, the piece 4, and the irregular curve shaped bottomwall 5, constitute the housing `of the regulatorthe upper part of the regulator, in the shape of aquadrant, is the compartmenthousing the retarder I3, andthe lower part isrthe vhousing forv the damper l2 and the airpasageway. The

owing air'enters `at the rectangular inlet 9 and leaves or is exhausted from the rectangular outlet I0V as indicated. bythe respective'direction arrows. The top ofthe inlet lies in a plane'horizontalto thefaXis and forms a 45 degree angle with the damper wh'euthe damper is inits fully open position. Thus anappropriate space isprovided forfavorableaction on the front face `of the damper 'by Athe air to Ibe controlled. This inlet, as illustrated in Fig. v1, allows the inflowing air is passing through; sixth, toiprov'ide a means horizontally from the left; Fig. 2, an isometric v view of the angular shaped piece forming part of the 'regulator housing; Fig. 3, an isometric view of a separate piece used to form part of the reair to strike the whole front .face of the Vdamper vwhen vin its fully open `position and simultanelous'ly to enter the'initial restricted ifree area," in the same directionasvlthe direction of ow of the inflowing airas indicated by the direction arrow at 9.r The term restricted free area `as used in lthisfdescription refers `to the opening formed by the vtip or free edge of the damper, in-its various vpositions `as described hereafter, and the sides and bottom of the housing. 'This areal becomes tarder compartment andfpart of the rectangular outlet; Fig. 4 an isometric View of the counter- -balancing combined damper and retarder, with shaft, which, when assembled in the housing, is mounted in suitable` self-lubricating bearings :formed on the walls l, I; Fig. 5 represents a Ver- -tical section ofthe regulator, a little to the near Y Ibinding strips 14, .I4 which are drawn-tight with i side `ofrthe middle, indicating the operation of.

the damper and retarder when a counter'f'orce 'in the form of springs only is used in substitution for .the weighted cam and auxiliary spring as shown in Fig. 1; Eig. 6 is an enlarged sectional v iewof the parts in the Vicinity of the shaft Il Villustrating how-the strips 2| and 22 partially close the -space lengthwise with the shaft. Figs; 7 rand 8 -are enlarged views illustrating how Athe A'cam 15 is developed. And Fig. 9 represents ,a

more and more restricted `as the damper moves to the right towards its maximum flowrestricting position as, shownin Fig.` 5.

' A stiff `and corrosion-resistant shaft# l I, ksmall in diameter, ts intoV the long khole formed in the light-weight, corrosion-resistant, laminated sheetsconstituting Vthe counterbalancing com-Vv Y bineddamper l2 and retarder I3,.and is held by screws, supplemented, if need be, by coating the shaft with pulverized rosin to give additionalbite.

The `s'haftis the axis of the damperflz at ritsA 'top edge as wu as the axis of the 'retarder la (at its bottom edge,randwis Aso considered, notwithstanding that the' top edge of the damper 4 and the Zbottom edge of the retarder may bejoined together vas shown in Fig.` v4`andY no edge is ap.

parenti x Y On vone end of the shaft-'lul and fastened to it. iis a light-weight, counterbalanced YV-flanged, spi- -rally shaped cam 15,-fromwhichis suspended a .Weight ll'rby the flexible cable T1, and ,to the right is the cams-auxiliary spring I8 fastened tov Vvertical 'section of an inferior for-m of regulator the side ofthe housing by the clamping bracketV IB-L and this cam, weight, cable and spring may be protected by being enclosed with a side cap. The position of the cam when the damper is partly closed is indicated at I5-I and when Al5 closed is indicated at I5-2. Y

In Fig. 5, I2 represents the position of the damper when the ldamper is fully open. The broken lines ',I2--IV radiating downward from the axis, from 111A degresto 90 degrees, represent the position of the damper in varying positions of closure 11%. degrees apart; and, I3 and the broken lines I3-I radiating upward from the axis represent corresponding positions of the retarder. Also indicated in Fig. 5 is the opera- 15 tion of the regulator when used with springs as Y the counterforce instead of the cam and auxiliary spring. Line 24 represents `a long, Yslightly curved, flat spring fastened to the housing at 23 and the curving broken line 25 represents the po- 20 sition of thisrspring when the damper is in its closed position; the curving ,line 24e-2 is the line upon which is measured the deection and estimated power of the spring. i The second and f.

, third springs 26 and ZIarelOcatedabout as shown 25 f andi placed onebeside the other, but act irrtandem, and are respectively clampedto the housing as indicated at. 28. When the damper uis atY maximum open posiff f tion its freeedgeis directed; toward the inlet, in 30,.

which position vthe damper is at an angle of 45 degrees with an imaginary line from the Vaxis of v the damper to the'bottom wall,` at right angles to v the direction of flow of the inowing air, th'edi-Y rection ofow being as indicated by the direction arrow at 9. :In Ythis position the damper is fully.V open. j Asthe damper moves backward through f. anarcof 90 degrees it restricts the free area more and more. When itY reaches 90 degrees itv canf:

move.baok no-further. i In this'position "it is in itsmaximum flow restricting position and is also considered as closed- However, preferably, the

passageway is not entirely shutoi.V The distance of the opening'remainingwhen the ldamper is infY its maximumA iiowfrestricting position is, prefer- 45l ably, approximately ,1/6 the distance of the opening when the'damp'er is at its maximum open position, as indicated in Fig. 5. i-In some circumstances,the,nal distance caribe more or less than the or `can be v`nodistance, as may' best 50 suit the purpose to beserve'd. 3V f VThe dimensions and proportions ofthe regulato'r as illustrated in Fig. '1 and described in this `specification are as follows: theinitial'restricted f position, referred toas the-initial restricted free area, the area of which is made equal in square feetto the desired capacity (quantity) in. cubic feet of air per minute divided by the desired de-" -livered velocity of'thegair inifeet per minute. 7W Thatis, A equals Q/Vz` And, observing the preferred rule that the'area be twice as wide as deep', the dimensions of -this area can be cal- -culated byj making-thedepth (D) equal to the?A square root of 1/zrthe area; that is, D equals the 75 `fect circle.

square root of 1/A. However, the maximum uid velocity to be provided for in a single regulator should ynot exceed, preferably, eight times the desired delivered velocity, on the basis of the clearance space, when 'the damper is in its maximum flowrestricting position, being one-eighth of the initial restricted free area. For a greater rang of velocitythan would thus be provided for,

two suitably devised regulators should be used in series.'

The shape of the bottom 5 and the degree of reduction of the free area caused by the upward curve of the bottom, from the 0 degree position to the 90 degree position, is tentatively determined as follows: The distance between the free edge of the damper when in its maximum flow restricting position, as described above, and thebottom isselected. This distance is then subtracted from the distance between the free edge of the Adamper when fully open, vas described above, andthe bottom. Y The diierence is `the distancethat has tobe gradually reduced. The differenceis divided by 8, the number off'Il 1/4 degree divisions. This iigure is then used as the constant differenceV to be subtracted in an arithmetical progression to reduce the distance gradually at eachfV of the 8 division points.

However, tof provide a bottom Wall whichis more symmetrical and betteradapted to permit the llowroofY air at low velocity with a minimum loss of Velocity,the bottom is actually formed by varying slightlyrfrom the ascertained'respective A distances described above. AI usethe ascertained Y respective distances asa guide in forming acom- 5 promising irregular curve vof easier changefor Y the'bottom wall. The foregoing description providesY a methodwhereby the dimensions of any sizeof housing and damper may be determined without resorting to experimentation,V .leaving -only the jvar-ying value of the'counterforce tobe Y determined partially by experimentation.

Inferior forms of thehousingcan be designed toaccommodate` the damper positioned so that its Yfree edge'would be directed toward the inlet atan angle less than the preferred 45 degrees be- 1 fore mentioned when the` damper is vin its.v full open position, or to'v accommodate the damper swinging through an arc of less 'than the pre-` ferred 90 degrees shown in Figs. 1 and 5, oreven to accommodate the damper positioned so that it is atvright angles to the direction of ow of the inflowing air when in its full open position as ili lustrated in Fig. 9, byascertaining the respective l Vdistances which ishould exist between` the free edge of the damper and the bottom wall as before described, but, instead of the irregular curve havingradii as illustrated in Fig. 1 the respective distance points would be connected together with draftsmen.' An irregular curve comprises two or A more regular curves of different radii. A regular curve is considered as being a segment of a per- The damper I'2, hanging plumb, as shown in1.ig.9,V doesnot necessarily have to be balanced under static conditions. It can be un- `dercounterweightedtas indicated at l38 in Fig. 9

orit need not becounterweighted because a coununder-counterweighted vor not counterweighted.

.Y Ifthe damper of an air flow regulator, such as Ais here described is counterweighted so that the damper is lessthan counterbalanced, `i.!e., undercounterweightedfthe excess Weightof the damper constitutes'part of the counterforce mentioned'in this specification.

'This housing, with suitable bearings and a suitable counterforce, is adaptablelfor luse in almost any practical position different from ythat illus- .trated in Fig. 1, including that of the housing being equivalently arranged so the axis of the damper may be vertical. However, any range of regulation of less than 80 degrees would, for various reasons, be so disadvantageous as to be impractical for general use. f

Such a contracting bottom forms, in tion With the swing of the free edge of .the damper, a free area which suitably reduces as the velocityof the lair increases. Furthermore, such a reducing free area can be conveniently spacedhere at intervals of lllrdegrees-for the purpose of making computations to determine the calculated velocities at each of the division points. This may be done Yby dividing the ca,- pacity of the regulator in cubic feet of air. per minute by the area of therespective openings at the division points in square feet.

The damper is considered as being activated by the force due to the velocity of the incoming air striking the front face of the damperacting against the resisting counterforce of the Weighted cam l5 and its auxiliary spring I8, even if kthe normal or natural pressure at the rear of the damper is diminished by suction at the outlet of the regulator. VBeginning with the initial restricted free area, when theD damper is in its fully open position, I calculate the velocity of the air to increase, at each of the respective 11i/(degree conjunc- "age exertedfbythe air acting onthe damper corx positions of the damper, in the same yratio as the corresponding free area decreases. (For exfree area is halved.) InY other Words, if the distance from the free edge of the damper, When in lits initial or fully open position, tothe'bottom Were 8 inches, and the width of the area were `16 inches, there Would be 128 square inches or .889 square foot of free area. If the desired capacity (quantity) is-177 .8 cubic feet of air perrminute, I divide the177.8 by .889 squarefoot and find the initial calculated velocity to be 200 feet per minute, using the formula V equals Q/ A. Then if at the second position Yof the damper, 11%, vdegrees to the right, the height of theA free area i`s reduced from the initial 8 inches to7 inches, I multiply 7 by 16, the Width, to get the area at that position-112 square inches or-.78 of a square foot. This I divideinto the 177.8 cubic feet and find the calculated velocity to be 228 feet per minute; and so on in like manner at each of the suc- `ceeding 111/4 degree divisions until the damper nears its closed position. However, to` compensate for various factors of loss,rthere would have to be added to the calculated ,velocities a `considerable varying percentage, ascertainable by experiment, to more nearly approximate theac-` tual velocities: The velocities of the air, Whether calculated or actualare convertible into corresponding ounces of pressure per. square inch, and,

minute.

.of5ea`ch end: of its shaft, remain stationary at Vany positi'on'in which it Vmight be placed: lIn Figs. 1

and 4 the shaft is Ashovvn as being locate'dhorizon- :tally-which vshaft being supported, not by needle points, but by bearings around theoutside of the `small diameter shaft causes a slight static unbalance that is negligible; and the Vdamper l2 scon- 'sideredras being Vevenly counterbalanced bythe 'retarder -'|3`. n The damper may be counterb-alanced otherwise 'than by theY retarder.

-Thefarrange'ment vvherebythe free edgeof the Inferior results statically balanced 'dampenjWhen kin itsfully open position, with its free edge 'directed towardthe inlet, as before described, .in a housing having a rectangular, sloping .or other practicably shaped bottom. 'I i In 4,the'form of 'counterforce asillustrated, in Fig. 1,Y the preferred leverage distance from the axis to the useful starting point offthe curvature -of the cam and 'the amount of weight attached thereto .by the cable are made to bel equal, as resisting counterforce, tothe inch-ounces of Yleverrespondingto the actual velocity of the air at which the desired 4volur'n'eof air passes when the ldamper is in its ffull open position, and thus holds the damper to its fully `open positionguntil the quantity of .air passing nears `or slightly exce'eds the desired quantity.` Then, as theY force of the f air increases, moving the' damperV toward its closed position,Y the cam, as it turns, pushes over'the Weighted cable to a lengthened horizon- Y tal distanceY from the axis, to such an extent yas to constitute a resistance equal to the increased force of the air acting on the damperjthus there is equilibrium and the damper isheld to the positionvdueft'o such force; theincrease in resisting Ycounterlorcejis made to correspond reciprocally 'to any varying increase inthe force Yof theI airy throughout the whole range -ofregulation, for

about the V'lrst 56%, degreesby the Weighted cam only* and thereafter with theY auxiliary spring lbearing on the cam. 'Thecam as shownin Fig. 1 is-abbreviated at itsouter endVnecessitatingvthe use of an auxiliary spring;'however, a cam `could `be devised which, with only the Weight, would furnish' (the counterforce for the whole range of s regulation, but Iprefer the form as shown.

For the purposeof providing ameans by which the dimensions of the cam and the value of its auxiliary 'spring may 'finally be determined, Athe inlet 9 is supplied-With air 'of controllable `velocity the flowing air; this ductV v shouldlbe in length ten tir'nesV the mean Vdimensions, of "the outletl, and havein it anV egg crate typ ofi air straight; r ener such as is prescribedin the' Standard Test Y Codey of/ the ANational Association of FanManuLr .that is nearly equal in pressure over the Whole area'ogf` the inlet 9, then al45 degree angle tting. of'longradi'u's is connected tothe outlet lb, to

' direct the flow of air'horizontally, and to thisV fitting isy connected a test duct of the same dimensions as the outlet l-, tovequalize and straighten facturrs-asadopted by the 'American Societyfof '-Heating'andventilating Engineers.Y At or near maybe had by utilizing theV the end of this test duct readings aref-taken to Y indicate when the desired velocity of airl is being delivered Y ,f

VTo determine the value of counterforce to be furnished, I use, as in Figs. 7 and 8 a light weight balanced disc 29, the lower portion-of which disc Astation point 3| on the disc a horizontal distance 32Vfrom the axisV equal to, say, one-sixteenth the depth of the damper, or such4 other distance as may be necessary to provide-for the desired initial velocity of air; for example, in Fig. 7 the distance is yindicated as being .5"; andv this distance when arithmetically multiplied by the amount of weight to be hung therefrom will constitute the resisting counterforce in inchounces at this station. At this station, 3l set in the disc a screw of small diameter and a balancing screw at 3l-I. 'From this vfirst station is hung,rtentatively, suicient weight on the'cable `I1.to equal the calculated inch-ounces of leverage exerted by the damper I2 on the axis when the desired velocity is supposedly being delivered by the regulator while the damper remainsin curvature of the actual cam is made in accordance withV this curve to the extent to which the cam is not abbreviated; and the spring I 8 is designed to furnish the supplementing counterforce in accordance with the data ascertainable as above described.

The kind of counterforce illustrated in Fig. 1 is preferable if the most accurate regulation is required and if it is known in advance what position the regulator is to be used in; It is desirable to first make this form of counterforce in order to get the information from which to determine the modifications necessary to construct a counterforce such as the spring type illustrated inFig. 5. y

The spring type counterforce, consisting of the springs 24, 26, and 21, illustrated in Fig. 5,

Y is a modification of that illustrated in Fig. 1

its fullopen position at V0 degreespafter which v the added and exact amount of weight required is determined upon, and used thereafter, by air velocity readings to be takennear or at the end 'of the test duct above mentioned. From this rst station point score a plumb line 33 down a short distance on the disc. The'second station point on the disc is found by increasingthe supply of V air to the inlet ofthe regulator so that the damper will move toits 11% degree position as in Fig. 8; then compute the'inch-ounces of leverage exerted by the damper on the axis corresponding tothecalculated increased velocity of Y the air at that position and divide those inchounces of leverage by the ounces of Weight now on the cable, which will indicate the horizontal distance from the axis in inches or fractions at which the second station pointshould be tentatively located on the plumb line 33 in its changed, angular location, and this distance is measured ,horizontally from an unscored plumb line 35v scored on the side of' the regulator below the' bottom of the scale: on thisvdisc-the readings are taken by observing the location thereon` of the weighted cable I1. From` the actual'second station point 36 score a plumb-line 31 'down a short distance on the disc, upon which the next succeeding station is to be located. Proceeding in like manner for as many of the degree divisions indicated in Figures '1 and 8 as maybe necessary to answer the desired purpose. station points having thus been determined, ,the screws arey removed and the station points connected together by a perfect irregular (French) curve'in one continuousunbroken line, andthe The in that springs only are used and is preferred when only approximate regulation is needed because it can .be used with the regulator in almost any practical position; the shaft of the damper-retarder can be either horizontal or vertical. Thesprings are designed to perform the same function, as nearly as possible, as the weighted cam with its auxiliary spring. The first Vspring 24 is estimatedto furnish the same counterforce, as nearly as practicable, as the weighted camy does when the damper is at 0 degree lposition and :at subsequent positions until the damper reaches a point midway between the 33%.and 45 degree positions. When the damper is at this point, the second spring 2'6 begins to add to the counterforce. As the damper moves further towards the 90 degree position, the third spring 21 begins to add to the counterforce. Y

The counterbalancing retarder I3 rigidly attached to the damper l2 at the shaft Il is oscillative in its Ycompartment and functions as a dash-pot, as ordinarily understood, for cushioning the movement of the damper. The compartment in which the retarder is located is tightly enclosed except along the shaft Il where the opening is closedY as much as is practicable by )sheet metal strips 2| and 22 extending the Whole width of the regulator, as indicated in Fig. 6. The enclosed compartment confines the air, with the result that the retarder, before it can move forward, has to compress the air in front of it sufficiently to force the air past the tip of the strip 2| and to rarefy the air behind it sufliciently to cause air to enter past the tip of the strip 22. It is restrained in its backward movement by the reverse of this action. T' f ,The retarder may, less preferably, be connected Y to the damper otherwise than as shown in the drawings.

Such a retarding means is adaptable not only to a regulator as illustrated in Fig. 1, but is adaptable to other forms of regulator inv which a damper is activated by the force due to the velocity of natural flowing air.

VThe Words air, air flow and such like expressions as used in the specifications are synonymous with fluid, uid iiow and such like expressions as used in the claims; and activating-air means air flow whether acting as a pressure at the inlet of the regulator or as suction at the outlet of the regulator. Having described and illustrated one form and two modifications of -my invention, I wish it to be Y Zunderstood that my invention is not to be limited to the specific form or arrangement of parts herein described and shown, except in so far as width of the passage pivoted adjacent said oppo- A site wall and arranged to swing through anl arc` approaching ninety degrees toward said outlet by the force due to the velocity of the fluid entere ing said inlet, counterbalance means arranged to balance the damper under static conditions,

of the damper under flow conditions andmaintainY the damper with itsl free edge directed toward said inlet and for-ming with' the inflowing air an angle approaching forty-five degrees under minimum fluid velocity conditions, the curvature regulator including a passage` forty-,five degrees and not. exceeding approximately ninety degrees towards,` said outlet, with a housingV arranged 'to accommodate the' said damper and'having` a pairlofl oppositely disposed walls'onejof whichv approaches towards its opposite wall ina direction` towards said outletas an irregular curve comprising two or more segments of a circle of different radii, the curvature of the wall andthe said counterforce means Abeing so coordinated thatthe-product of the area, formed lnetweenv the freefedge of the da'mperand the of the wall and the counterforce means being so coordinated that the product of the area, formed between the free edge of the damper and the curved Wall at fluid velocities in `excess of the minimum; and the velocity producing such area is maintained substantially constant.

2. A fluid ow regulator includingha passage having an inlet at one end, an outlet at its other end and a pair of oppositely disposed walls one4 of which approaches as an irrgular curve towards said opposite wall ina direction towards the outlet, a damper having a width substantially equal to the width of the passage pivoted adjacent said opposite wall and arrangedI to swing through any predetermined'arc of not less than forty-ve degrees and not exceeding approximately ninety degrees toward said outlet by the Y 'force' due to the velocity ofthe fluid entering said inlet, counterbalance means arranged to balance the damper under static conditions, counterf force means arranged to resist movement of the damper under now conditions and maintain the.

damper` with its free edge directed toward said inlet and forming with an imaginary line from the axis of the damper to the curved wall at right angles to the direction of ow ofv4 the inflow-A ing air any predetermined angle of not less than twenty-two and one half degrees and not exceeding approximately forty-five degrees under minimum iiuid velocity conditions, the curvature of the wall and the counterforce means being so coordinated that the product of the area, formed between the free edge of the damper andthe curved wall at fluid velocities 'in eXces'sof the minimum, and the velocity producing such area is maintained substantially constant, all substantially as set forth. f i

3. In a uid flow regulator of the class wherein the regulator includes a passage having an inlet at one end, an outlet at itsother end and a pair of oppositely. disposed walls one of which approaches towards said oppositewall in a direction towards the outlet, a damper having a width substantially equal to the Vwidth of the passage pivoted adjacent said'opposite wall and arranged to swing toward said outlet by the force due tothe velocity of the uid entering said inlet, and counterforce means arranged to lresist movement ei the damper under flow conditions and maintain the damper in its full open'position under minimum uid velocity conditions, the combination of a damper arranged to swing counterforce means arranged to resist movement Y curvedwall at uid velocities in excess of the minimum, and-the velocity producing such area is, .maintained substantially constant, substantially as described.

'tor includingv also a counterweight means arrangedto counterweight the: damper. l '5; In a fluid now regulatorof the class whereinthe regulatorl includes a passage havinghan inlet at one end, an outlet at its other end and a pairof oppositely disposedwalls one of which approaches towards said opposite wall in a direction towards the outlet, a'damper having a width substantially equal to the width of the passage pivoted adjacent said opposite wall and arranged to swing toward said outlet by the force due to the velocity of the fluid entering said inlet, Jand a counterforce means arranged to resist movement of the damper under flow conditions so that the quantity of fluid flowing through the regulator remains substantially constant until the @damper nears its closed position at iluid velocities in excess of the minimum, the combination with said damper of a counterbalance means arranged to balance thedamper `understatic conditions and the damper arranged, inconjunction'with said counterforce means, so that its free edge is directed toward the said inlet under vminimum fluid velocityr conditions and so that the damper may swing through any predetermined arc of not less than thirty degrees and not exceeding approximately ninety degrees toward said outlet at iluid velocities inv excess of the minimum, substantially as described. q q

6. In a fluid oW regulator of the class wherein the regulator includes'a passage having an inlet at one end, an outlet at its other end and a pair of oppositely disposed walls one of which approaches towardsr said opposite wall in a direction towards the outlet, a damper having a width 'substantially equal to the width of the passage pivoted adjacent said opposite wall and arranged to swing through anypredetermined arc of not-` less than thirty degrees and notk exceeding ap-4 proximately ninety degrees toward said outlet by the force due to the velocity of the fluid entering said inlet, counterweight means arranged to,

counterweight the damper, and counterforce means arranged to resist movement of the damper under flow conditions so that the quantity oi fluid flowing through the regulator remains subthan one-sixteenth nor more than one-third of 'f the free area between the free edge of the damper and the said Wall when ythe damper is in its full open position, substantially as described.

' '7. In a fluid flow regulator of the classwhereir'i through any predetermined arcof not less than 1| the regulator includes apassage having an inlet l4. A; fluidl flow regulator. as described andA claimedin claim 3, characterized bythe regulaat onelend, an''utlet at its other'end'and a pair of oppositely disposed Walls one of'which yapproaches towards said opposite wall in a direction towards the outlet, a damper having a width substantially equal to the Width of the passage pivotedadjacent said opposite wall and arranged ssazc Y v would be cushioned .when the ldamper is subject to fluctuations by the activating air,substantial1y to swing toward said outlet vby the force due to tlflevelocity ofthe fluid entering said inlet, coun-l tervveight means arranged to counterweight the dax'rnpers .and a counterforce means arranged to resist movement ofthe damper under ow conditions so -l that the quantity ofud flowing through the regulator remains substantially constant until the damper nears its closed position at fluid velocities in excess of the minimum, the combination with said Vdamper of an oscillative blade operatively attached tothe damper, and a compartment .t'o :enclose the blade in its range of oscillation, 'said compartment Vhaving restricted L openings for retarding the entrance and escape of air,iwhereby the movement of the damper as described. Y. Y i Y 8. A fluid flow regulator including a housing, an oscillativedampena counterforce means integrated with said damper and so arranged tol Y) of oscillation, said compartment having restrictedV "openings for retarding'the entrance and escape of ar,"sc that the movementof the damper would be cushioned when the damper is subject to fluctuation by the activating air, substantially as described.Y Y Y Y Y GEORGE T. SIMPSON. 

